Could Eating Peanuts While Pregnant Cause Allergies?

For decades, experts have gone back and forth on whether infant feeding practices can affect the risk of a child developing food allergies, and despite a growing body of research, definitive guidelines remain elusive. Even less evidence is available to address a related question: can a woman’s diet during pregnancy play a role in her child’s food allergy risk? Recently, an observational study was published in the Journal of Allergy and Clinical Immunology, seeking to shed some light on this very question.

In this study, the research team was specifically interested in whether a mother’s consumption of peanuts during pregnancy might influence her child’s risk of developing peanut allergy. They looked at 503 infants (average age 9 months) who already had a convincing history of food allergy to either eggs or milk. Importantly, the subjects were not a random sample, but rather a group that would be considered “high risk” for food allergy, both because the infants already demonstrated signs of allergy to at least one food, and because the majority of their parents had a history of allergic disease (67% of moms and 60% of dads), itself a risk factor for developing food allergy.

Blood samples were drawn from the infants to test for the presence of “IgE” antibodies to peanuts above a threshold level that the researchers assumed would indicate a high risk (70%) of developing peanut allergy, based on studies of older children. At this time, there is no data to validate whether this threshold is equally predictive of peanut allergy risk in infants. They also recorded dietary patterns of the mothers during pregnancy, and divided them into groups based on frequency of peanut consumption: infrequent (less than twice per week) and frequent (twice per week or more).

The analysis revealed that the infants born to moms who ate peanuts frequently during pregnancy were about 3 times more likely to have elevated levels of peanut antibodies compared to infants of moms who ate peanuts infrequently during pregnancy. Because the presence of elevated antibody levels is not the same as a confirmed peanut allergy, the authors caution that following these children over time is the only way to know whether these results truly suggest a relationship between higher peanut consumption during pregnancy and a higher risk of developing an actual peanut allergy. The presence of elevated blood levels of peanut antibodies was even higher among infants of moms who frequently ate peanuts while pregnant but were never breastfed compared to those who were breastfed.

It would be premature to draw any sweeping conclusions for the general population of pregnant women, given that (1) the subject pool was one predisposed to developing peanut allergy, and (2) the study did not actually measure the development of a confirmed, clinical peanut allergy. Indeed, a previous study that looked at women and children from the general population (not a specifically high-risk group) found no association between maternal peanut consumption in pregnancy and the risk of having a clinically-verified peanut allergy in her children, though the analysis was limited to a subset of only 48 children.

Nonetheless, this new research raises important questions about whether pregnant women who might be considered high risk for having food-allergic children based on their own or their partners’ history of allergic disease could protect their unborn children from developing peanut allergy by avoiding peanuts during pregnancy. The controversy continues, and until more research is available to shed light on this vexing question, expert authorities offer no guidelines in either direction on maternal diet for the prevention of food allergy in children.